In general, the position of a wafer stage or reticle stage provided to an exposure apparatus is measured by a laser interferometer. It is known that the measurement accuracy of the laser interferometer is decreased by the temperature fluctuation (variation) of the optical path of measurement light. In order to suppress the temperature fluctuation, a technique is available which controls the temperature of a refrigerant by circulating the refrigerant in the surface of a heat-generating member arranged in the vicinity of a space where the measurement light is guided, thereby decreasing the temperature fluctuation of the optical path.
A technique is also available which supplies temperature-controlled gas to a space where measurement light is guided (for example, Japanese Patent Laid-Open No. 2002-008971), thereby decreasing the temperature fluctuation of the optical path.
When the refrigerant is circulated in the surface of the heat-generating member as described above, as the quantity of generated heat increases, the flow rate of the refrigerant to be circulated must also be increased. If the flow rate of the refrigerant increases, however, the pressure acting on a pipe or cooling jacket to supply the refrigerant increases. For this reason, the pipe wall must be increased so the pressure will not break the pipe or cooling jacket (to be referred to as a pipe or the like hereinafter). Particularly, when the heat-generating member is a linear motor coil, if the pipe wall increases, the distance between the coil and a magnet increases to decrease the thrust. If the flow rate of the refrigerant increases, the flow of the refrigerant may induce the vibration of the pipe or the like. This is because when the flow rate of the refrigerant increases, the flow of the refrigerant becomes turbulence. Such vibration serves as a disturbance to the control system of an alignment apparatus such as a linear motor.
As described above, when temperature-controlled gas is supplied to a space where measurement light is guided, if the flow rate of the gas increases, the filter may produce dust. When the temperature-controlled gas is to be supplied in an exposure apparatus, it is generally done so through a filter. The filter generally has a regulated velocity. If the flow rate exceeds the regulated velocity, the filter produces dust. Even when no filter is used, if the flow rate of the gas is increased, it induces vibration of the pipe or the like employed to circulate the gas. When the velocity of the gas is further increased, a negative pressure is generated where the gas flows, to involve surrounding gas, generating temperature fluctuation.